The wastewater from factories etc. includes various types of materials to be separated from the wastewater from the viewpoints of environmental protection and recycling of resources. For example, wastewater discharged from a recycled paper manufacturing plant may include many materials to be separated such as dye and pigment contained in used paper, organic matter contained in adhesive, and coagulant added during conventional wastewater treatment. Since these substances are causative agents that raise COD (Chemical Oxygen Demand), the discharge of such substances has been strictly regulated recently for environmental protection. Similarly, with reference to not only the index of COD, but also indexes of BOD (Biochemical Oxygen Demand) and TOC (Total Organic Carbon), the discharge of causative agents that raise these indexes should be regulated from the viewpoint of environmental conservation.
In conventional wastewater treatment, after normal treatment using coagulant, biological treatment is performed using activated sludge. Specifically, organic matter contained in the wastewater is degraded by a variety of bacterium or aggregations of organisms (activated sludge) and then discharged.
The prior art documents related to the invention of the patent application include for example the following: Japanese Patent Publication No. 2002-292565; Japanese Patent Publication No. 2002-210311; Japanese Patent Publication No. 2002-180101; Japanese Patent Publication No. 2002-292305; Japanese Patent Publication No. 2002-316068; Japanese Patent Publication No. 2002-316069; and Japanese Patent Publication No. 2002-316067.